On the electrorefining of copper, the copper in a purified state is electrodeposited upon a cathode in any electrolyte which contains generally about:
20 gams per liter of nickel ion, PA1 4 grams per liter arsenic ion, PA1 0.5 grams per liter antimony, PA1 0.18 grams per liter cobalt, PA1 0.10 grams per liter iron, PA1 0.11 grams per liter manganese PA1 0.17 grams per liter zinc PA1 0.018 grams per liter lead, PA1 0.39 grams per liter sodium, PA1 0.012 grams per liter potassium, PA1 0.13 grams per liter magnesium and PA1 0.31 grams per liter calcium.
The copper content of the bath can be about 42 grams per liter while the sulphuric acid content or sulphate iron content can be about 180 grams per liter.
When copper is electrorefined in this manner, the cathodes are removed from the bath from time to time and are subjected to further processing.
Upon the removal of the cathodes from the electrolyte, electrolyte tends to adhere to the surface and, during the smelting of the cathode, a portion of the impurities which originally accrued from the electrolyte can be found in the melt and in the ingots cast therefrom. In other words, a portion of the impurities in processed copper and hence objects fabricated therefrom, can be traced to substances which were originally picked up by the cathode in electrolyte which adheres to the surface thereof.
These impurities can amount to several percent of the total impurities in the processed metal.
This has been recognized in the past and hence considerable effort has gone into developing techniques for eliminating impurities adherent to the copper. Thus, the cathodes can be subjected to an intensive washing process which can include immersing the cathode in hot water, directing jets of steam or high pressure water against the cathode and the like.
These techniques have not been found to be fully satisfactory especially where the copper surface of the cathode is not completely smooth or continuous, i.e. where the copper contains cracks, protuberances, cavities or pin holes. Consequently, while the total impurities of electrolytic copper by conventional processes can amount to 20 to 50 parts per million of which several percent can be attributed to adherent electrolyte, the conventional washing methods normally eliminate only a fraction of the latter percentage.